、。
Singapore differs from Japan in that doctors there almost always all know each other.
Literal
Singapore [genitive-の] doctors [topic-は] most [genitive-の] cases everyone each-other [object-を] know, [quotative-というのが] Japan [and-と] differs.
A comparative cultural observation. 殆どの場合 (ほとんどのばあい, 'in most cases') sets the scope. 皆お互いを知っている ('everyone knows each other') describes the tight-knit medical community. というのが ('the fact that...') nominalizes the preceding clause as the subject of 異なる (ことなる, 'to differ'). 日本と異なります ('differs from Japan') makes the cross-cultural comparison. The sentence provides an outsider's observation about Singapore's medical profession relative to Japan's.